Construction of heaters

ABSTRACT

This invention describes the construction of heaters in which chemical process streams are heated by making a composite sheet having the developed length of the cylindrical heater. The composite sheet is then rolled up rather like a &#39;&#39;&#39;&#39;Swiss roll&#39;&#39;&#39;&#39; to a size suitable for transport. Then on site the composite sheet is unrolled to a cylindrical shape to form one cylindrical section of the heater, the latter being formed by stacking a number of such sections one upon another.

United States Patent 2,751,672 6/1956 Reed Filed lnventor Appl. No.

Patented Assignee CONSTRUCTION OF HEATERS 6 Claims, 7 Drawing Figs.

US. Cl 52/745, 29/429, 29/471.1, 29/480, 52/245 Int. Cl. E04b 1/35 Field of Search 29/429, 480, 471.1; 52/741 745, 749, 750, 245

7 References Cited UNITED STATES PATENTS Primary Examiner-Price C. Faw, Jr. Attorneys-John Maier, lll, Marvin A. Naigur and Constantine A. Michalos ABSTRACT: This invention describes the construction of heaters in which chemical process streams are heated by making a composite sheet having the developed length of the cylindrical heater. The composite sheet is then rolled up rather like a Swiss roll" to a size suitable for transport. Then on site the composite sheet is unrolled to a cylindrical shape to form one cylindrical section 'of the heater, the latter being formed by stacking a number of such sections one upon another.

PATENTEUHAY 4|97| 357K695 SHEET 1 OF '2 4 Inventor A Home y PATENTEDHAY 4mm 3,577,695

SHEET 2 (1F '2 I nuenlor A Home CONSTRUCTION or HEATERS BACKGROUND OF THE INVENTION This invention relates to the construction of heaters in which process streams are heated for later treatment and to the heaters so constructed.

These heaters generally comprise an upright cylindrical tower provided at or near its base with one or more burners. The cylindrical shell of the tower is lined with a refractory material and ='a number of upright tubes are positioned within the tower through which various process streams are fed for heating by radiant and convection heat by the hot gaseous combustion products. The tower itself is usually surmounted by a stack for the spent combustion gases.

The cylindrical tower is usually of relatively large size, and as an example the tower may be feet in diameter and 60 feet high. This large size makes it quite impossible to prefabricate the tower in the workshop and then shift it to the site in one piece. Therefore the tower has been constructed from a large number of curved plates which are lifted into position and then welded along vertical and horizontal seams to adjacent plates.

Such a method of construction is both costly, because it involves a great deal of onsite welding, and in any case the resulting welds are generally less satisfactory than welds made in the workshop, and time consuming because it is difficult to align the adjacent plates at all accurately.

The latter problem has been to some extent overcome by providing the edges of the plates with outwardly directed flanges and the adjacent flanges of adjacent plates are bolted to one another as a first step in assembly and thereafter the plates themselves are seal weldedto one another. Such a method of construction still involves as much onsite welding, however.

The invention has, therefore, been made with these problems in mind and it is an object. of the invention to reduce the amount of welding which has to be made onsite.

According to the invention the cylindrical tower is constructed by welding together a number of metal sheets to give a composite sheet which is of a length such that it can be bent to form a cylindrical subsection of the tower, rolling or coiling up the composite sheet in a way analogous to a Swiss roll' so that it has a diameter sufficiently small to enable it to be transported to the site, unrolling the composite sheet onsite to the diameter of the cylindrical subsection to be formed and welding together the adjacent edges of the composite sheet to form the cylindrical subsection which can then be used in the construction of the tower.

Working in this way, the number of welds to be made onsite is materially reduced and also those made in the workshop, besides being cheaper, can also be more accurately made and tested.

According to another aspect of the invention there is provided a rolled up composite sheet ready for transportation to a site which comprises a number of metal sheets which have been welded together end-to-end to give the composite sheet which has then been rolled up in a manner analogous to a Swiss roll" so asto have a sufficiently small diameter to enable it to be transported to the site.

According to a further feature of the invention there is provided a heater which includes an upright tower made by stacking a number of preformed cylindrical subsections one on top of another and joining adjacent subsections, each section having been formed from a number of plates welded to one another in theworkshop so as to form a composite sheet, the free ends of which have been welded to one another onsite to give a cylindrical subsection of the required diameter, and each section having adjacent its upper and lower edges annular strengthening members which retain the section in its substantially cylindrical shape.

It will be appreciated that an important advantage of this method of construction is that a great deal of prefabrication can be effected in the workshop and that onsite the formation of a cylindrical section from the rolled-up sheet can be proceeding while a completed section is hoisted into place and fixed. The work onsite can therefore proceed more quickly than before and also the construction of the tower is made more independent of the weather conditions than was previously possible.

The sheets which are welded together in the workshop can initially be flat or curved either to the final diameter or some other diameter. Once they have been welded together, the resulting composite sheet can then be rolled up to a diameter suitable for shippingFor metal plates of three-sixteenths inch thickness or less, it may be possible to roll up the composite sheet without first giving the ends a curved shape whereas for thicker sheets the ends of the composite sheets may have to be given a preshaping before rolling up.

Also with thicker plates it may be necessary first to roll it to an intermediate diameter and then to repeat the rolling to achieve the final rolled up state for transporting. Once the composite sheet has been rolled to its shipping diameter the outer free end can be tack welded to prevent unrolling during transport.

The actual ways in which the composite sheet is rolled up to its Swiss roll shape and then partially unrolled to its final diameter are not critical. One simple way of unrolling the sheet onsite is to position it within upper and lower circular strengthening members and, starting at one end, the sheet is gradually brought into contact with these members and fixed to them by for example welding, and finally the free edges of the sheet are welded together. This method has the advantage that the circular strengthening members can also serve as flanges to hold-adjacent cylindrical sections together before welding.

DESCRIPTION OF THE DRAWINGS The invention will now be illustrated, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 shows a composite sheet;

FIG. 2 shows the rolled up composite sheet ready for transport;

FIG. 3 shows a shipping spider for use in supporting the rolled upsheet',

FIG. 4 shows the unrolling of the composite sheet during the preparation of a cylindrical section of the heater;

FIG. 5 is a plan view of the completed section;

FIG. 6 is an elevation of the completed section; and

FIG. 7 is a detail upright section showing the assembly of the completed sections one upon another.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1 of the drawings, a composite sheet S is prepared in the workshop by joining together a number of smaller metal sheets s by means of welds w. These welds can ofcourse be made relatively accurately in the workshop and can also be carefully tested. The sheets s may be flat or curved either to their final diameter or some other diameter. In order to assist rolling-up the ends of the sheet S may be given an initial curve to, for example, the radius R as shown in FIG. 1. The length l of the sheetS is the developed flat length which corresponds to the final circumference of the heater.

The sheet S is next rolled up to a Swiss roll shape r as shown in FIG. 2. The diameter d of this is less than the final diameter of the heater tower and is made small enough to meet the limitations required by the means of transporting to the site of erection. The sheet is held in its Swiss roll" shape by tack welds t formed between the free outer end 0 of the sheet S and-the adjacent convolution of the sheet. In addition the free inner end i of the sheet S can also be tack welded to the adjacent convolution of the sheet S if desired. This is not essential, however.

The sheet S can be rolled up in any suitable way. For example, a number of steel hawsers can be passed around the sheet having curved ends as shown in FIG. 1 and then pulled until the sheet is rolled up sufficientlyv For protection during transport, the sheet S in its Swiss roll" shape r can have inserted within it a shipping spider a as shown in FIG. 3. This is not essential, however.

If desired the coiled up sheet S can have small lifting lugs fitted to it for ease of handling during transportation. These can then be removed onsite.

Once at the site the tack welds t are cut and the sheet S is unrolled to its final diameter and its free ends and i welded together by means of an upright weld W (FIG. 6).

One suitable method of unrolling the roll is shown in FIGS. 4 and 5. The sheet S in its Swiss roll shape r is positioned inside upper and lower circular flanges F. Then starting from the free outer end 0 of the sheet S it is gradually unrolled and welded to the flanges F, until it has been welded to the flanges completely around their periphery as shown in FIG. 5. Finally the two free ends of the sheet are joined together by the upright seam weld W.

The finished cylindrical subsection B is shown in elevation in FIG. 6. Preferably one or both of the Flanges F project beyond the edge of the cylindrical sheet S so that, when one finished section B is placed on top of another, a small gap g (FIG. 7) is left for a full strength seal weld g w to be made between the adjacent edges of the plates S of the sections B. In the embodiment shown in FIG. 7 the flange F, coincides with the lower edge of the sheet 5 but the other flange F is spaced slightly outwardly of the upper edge of the sheet S.

The heater is made by assembling a number of these sections B one upon the other. Initially a finished section B is placed on another section and they are fixed temporarily by bolting adjacent flanges F together by bolts passed through holes h in the flanges (FIGS. 5 and 6). Then the peripheral weld g w is made as shown in FIG. 7 to complete the heater.

Since the diameter of the flanges F may be too large to be transported from the workshop to the site, they can be fabricated onsite by welding together say 4 quadrant parts.

As will be appreciated the amount of welding to be made onsite is much reduced and also the speed of assembly of a heater onsite can be considerably increased which is very important because any work made onsite is considerably more costly than if effected in the workshop.

A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

lclaim:

1. A method of constructing the cylindrical tower of a heater comprising the steps of:

A. assembling a number of metal sheets end-to-end,

B. welding the adjacent edges of adjacent sheets together so as to form a composite rectangular sheet which is of a length such that it can be bent to form a cylindrical subsection of the tower,

C. forming said composite sheet into a roll to enable it to be transported to an assembly site,

D. unrolling said composite sheet onsite to the diameter'of said cylindrical subsection to be formed,

E. welding together adjacent free ends of said composite sheet to form said cylindrical subsection,

F. stacking said cylindrical subsection so formed on another subsection, and

G. joining said subsections to one another along their adjacent peripheral edges.

2. In the construction of a cylindrical tower for a heater made up by stacking a number of cylindrical subsections one upon another, the steps of forming a rectangular composite sheet from a number of smaller metal plates in a workshop, rolling up said composite sheet into a roll of a diameter suitable for transportation to the assembly site, transporting said rolled up sheet to said assembly site, and forming a cylindrical subsection from said composite sheet by partially unrolling said rolled up sheet and joining its free ends together.

3. A method of constructing the cylindrical tower of a heater comprising the steps of:

A. assembling a number of metal sheets end-to-end,

B. welding the adjacent edges of adjacent sheets together so as to form a composite sheet which is of a length such that it can be bent to form a cylindrical subsection of the tower,

C giving the free end portions of said composite sheet an initial curve,

D. forming said composite sheet into a roll to enable it to be transported to an assembly site, by passing a number of steel hawsers around the sheet and pulling said hawsers tight until said sheet is rolled up sufficiently,

E. unrolling said composite sheet onsite to the diameter of said cylindrical subsection to be formed,

F. welding together adjacent free ends of said composite sheet to form said cylindrical subsection,

G. stacking said cylindrical subsection so formed on another subsection, and

H. joining said subsections to one another along their adjacent peripheral edges.

4. A method of constructing the cylindrical tower of a heater comprising the steps of:

A. assembling a number of metal sheets end-to-end,

B. welding the adjacent edges of adjacent sheets together so as to form a composite sheet which is of a length such that it can be bent to form a cylindrical subsection of the tower,

C. forming said composite sheet into a roll to enable it to be transported to an assembly site,

D. welding the free outer end of said sheet and the adjacent convolution of said rolled up sheet to retain the sheet in its rolled up state prior to transportation,

E. unrolling said composite sheet onsite to the diameter of said cylindrical subsection to be formed,

F. welding together adjacent free ends of said composite sheet to form said cylindrical subsection,

G. stacking said cylindrical subsection so formed on another subsection, and

H. joining said subsections to one another along their adjacent peripheral edges.

5. A method of constructing the cylindrical tower of a heater comprising the steps of:

A. assembling a number of metal sheets end-to-end,

B. welding the adjacent edges of adjacent sheets together so as to form a composite rectangular sheet which is of a length such that it can be bent to form a cylindrical subsection of the tower,

C. forming said composite sheet to enable it to be transported to an assembly site,

D. unrolling said composite sheet onsite to the diameter of said cylindrical subsection to be formed by positioning it within upper and lower circular strengthening members and, starting at the free outer end of said sheet, progressively unrolling said composite sheet and progressively joining it to said members around their circumference,

E. welding together adjacent free ends of said composite sheet to form said cylindrical subsection,

F. stacking said cylindrical subsection so formed on another subsection, and

G. joining said'subsections to one another along their adjacent peripheral edges.

6. A method according to claim 5 in which, when one subsection has been stacked on another, the adjacent strengthening members are joined together and then the adjacent peripheral edges of the composite sheets are welded to one another. 

1. A method of constructing the cylindrical tower of a heater comprising the steps of: A. assembling a number of metal sheets end-to-end, B. welding the adjacent edges of adjacent sheets together so as to form a composite rectangular sheet which is of a length such that it can be bent to form a cylindrical subsection of the tower, C. forming said composite sheet into a roll to enable it to be transported to an assembly site, D. unrolling said composite sheet onsite to the diameter of said cylindrical subsection to be formed, E. welding together adjacent free ends of said composite sheet to form said cylindrical subsection, F. stacking said cylindrical subsection so formed on another subsection, and G. joining said subsections to one another along their adjacent peripheral edges.
 2. In the construction of a cylindrical tower for a heater made up by stacking a number of cylindrical subsections one upon another, the steps of forming a rectangular composite sheet from a number of smaller metal plates in a workshop, rolling up said composite sheet into a roll of a diameter suitable for transportation to the assembly site, transporting said rolled up sheet to said assembly site, and forming a cylindrical subsection from said composite sheet by partially unrolling said rolled up sheet and joining its free ends together.
 3. A method of constructing the cylindrical tower of a heater comprising the steps of: A. assembling a number of metal sheets end-to-end, B. welding the adjacent edges of adjacent sheets together so as to form a composite sheet which is of a length such that it can be bent to form a cylindrical subsection of the tower, C. giving the free end portions of said composite sheet an initial curve, D. forming said composite sheet into a roll to enable it to be transported to an assembly site, by passing a number of steel hawsers around the sheet and pulling said hawsers tight until said sheet is rolled up sufficiently, E. unrolling said composite sheet onsite to the diameter of said cylindrical subsection to be formed, F. welding together adjacent free ends of said composite sheet to form said cylindrical subsection, G. stacking said cylindrical subsection so formed on another subsection, and H. joining said subsections to one another along their adjacent peripheral edges.
 4. A method of constructing the cylindrical tower of a heater comprising the steps of: A. assembling a number of metal sheets end-to-end, B. welding the adjacent edges of adjacent sheets together so as to form a composite sheet which is of a length such that it can be bent to form a cylindrical subsection of the tower, C. forming said composite sheet into a roll to enable it to be transported to an assembly site, D. welding the free outer end of said sheet and the adjacent convolution of said rolled up sheet to retain the sheet in its rolled up state prior to transportation, E. unrolling said composite sheet onsite to the diameter of said cylindrical subsection to be formed, F. welding together adjacent free ends of said composite sheet to form said cylindrical subsection, G. stacking said cylindrical subsection so formed on another subsection, and H. joining said subsections to one another along their adjacent peripheral edges.
 5. A method of constructing the cylindrical tower of a heater comprising the steps of: A. assembling a number of metal sheets end-to-end, B. welding the adjacent edges of adjacent sheets together so as to form a composite rectangular sheet which is of a length such that it can be bent to form a cylindrical subsection of the tower, C. forming said composite sheet to enable it to be transported to an assembly site, D. unrolling said composite sheet onsite to the diameter of said cylindrical subsection to be formed by positioning it within upper and lower circular strengthening members and, starting at the free outer end of said sheet, progressively unrolling said composite sheet and progressively joining it to said members around their circumference, E. welding together adjacent free ends of said composite sheet to form said cylindrical subsection, F. stacking said cylindrical subsection so formed on another subsection, and G. joining said subsections to one another along their adjacent peripheral edges.
 6. A method according to claim 5 in which, when one subsection has been stacked on another, the adjacent strengthening members are joined together and then the adjacent peripheral edges of the composite sheets are welded to one another. 